Image projection apparatus

ABSTRACT

An image projection apparatus includes a light source, light from which is used to form an image to be projected, a first flow path, a control unit configured to control a light emission from the light source, an electrical power stabilizing unit configured to stabilize an electrical power to be supplied to the light source, and an electrical power source unit configured to supply the electrical power to at least one of the control unit and the electrical power stabilizing unit. One or both of the electrical power source unit and the electrical power stabilizing unit is/are divided into a plurality of boards. The light source is arranged on a normal line of a surface of any of the plurality of boards. The plurality of boards configure surfaces of the first flow path except a surface nearest to the light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 14/454,416, filed Aug. 7, 2014, which is acontinuation application of U.S. application Ser. No. 13/660,289, filedOct. 25, 2012, which claims priority to Japanese Patent Application No.2011-242924 filed in Japan on Nov. 4, 2011. The entire contents of eachof the above are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image projection apparatus.

2. Description of the Related Art

Conventionally, there is known an image projection apparatus providedwith an image forming part to form an image with light emitted from alight source on the basis of image data from a personal computer (PC),video camera or the like, so that the image is projected and displayedon a screen or the like.

The image projector apparatus is provided with (i) a ballast board as anelectrical power stabilizer for supplying stabilized electrical power(electrical current) to the light source with an AC (Alternate Current)voltage corresponding to fluctuation of the light source, and (ii) a PFC(Power Factor Correction) power source board as a power source board forsupplying electrical power to a control board as a control unit forcontrolling the light source and the image forming part. For theelectrical power stabilizer and the control unit, the PFC power sourceboard boosts the AC voltage supplied from a power source cable. The PFCpower source board and the ballast board are provided with a greatnumber of electrical elements such as a capacitor, a coil, a resistorand the like. These electrical elements generate heat to raise thetemperature of boards. When the temperatures of the PFC power sourceboard and the ballast board rise and become high temperatures, theoperation performance and the durability may be lowered.

Japanese Patent Application Laid-open No. 2007-78924 discloses an imageprojection apparatus for blowing air to the PFC power source board tocool the PFC power source board by air.

However, a great number of electrical elements such as the capacitor,the coil and the resistor are mounted on the PFC power source board, asdescribed above, and thus the area of the board itself is large and itis long in the flowing direction of the air. As a result, the air, whichtook heat from the PFC power source board on the upstream side and whichtemperature rose, flows on the downstream side of a flow path of the airthat flows on the PFC power source board. A portion that is notsufficiently air-cooled thus may arise on the downstream side of theflow path of the air of the PFC power source board. The wind amount israised by raising the rotation number of a fan and the like serving asan air blowing unit for blowing air to the PFC power source board orusing a large fan so that the air of low temperature can also flow onthe downstream side of the flow path of the air of the PFC power sourceboard. However, if the rotation number of the air blowing unit israised, the wind noise increases, the noise of the apparatus increases,and the power consumption increases.

Furthermore, an area deviated from the flow path of the air of the airblowing unit may arise on the PFC power source board having a large areaand a portion that is not air-cooled may arise depending on the size andthe arrangement position of the air blowing unit such as a fan. Thus, alarge air blowing unit is required and the flow path of the air blown bythe air blowing unit needs to be made large, in which case, theapparatus enlarges. Furthermore, the PFC power source board has a largearea, as described above, and has a large volume since a great number ofelectrical elements are mounted thereon. Therefore, the PFC power sourceboard cannot be arranged in an open space after each optical element ofthe image projection apparatus is arranged, and a space for arrangingthe PFC power source board needs to be prepared anew. The mattersdescribed for the PFC power source board also goes for the ballastboard, and are the cause of enlargement of the apparatus.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

An image projection apparatus includes a light source, light from whichis used to form an image to be projected, a first flow path, a controlunit configured to control a light emission from the light source, anelectrical power stabilizing unit configured to stabilize an electricalpower to be supplied to the light source, and an electrical power sourceunit configured to supply the electrical power to at least one of thecontrol unit and the electrical power stabilizing unit. One or both ofthe electrical power source unit and the electrical power stabilizingunit is/are divided into a plurality of boards. The light source isarranged on a normal line of a surface of any of the plurality ofboards. The plurality of boards configure surfaces of the first flowpath except a surface nearest to the light source.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a projector and a projection plane according to an embodiment;

FIG. 2 is a view illustrating light paths from the projector to theprojection plane;

FIG. 3 is a perspective view schematically illustrating an internalstructure of the projector;

FIG. 4 is a perspective view schematically illustrating a light sourceunit;

FIG. 5 is a perspective view illustrating optical system componentshoused in a lighting unit, illustrating with other units;

FIG. 6 is a perspective view from a direction indicated by an arrow A inFIG. 5, schematically illustrating the lighting unit, a projection lensunit, and an image forming unit;

FIG. 7 is a perspective view illustrating light paths in the lightingunit;

FIG. 8 is a perspective view illustrating the image forming unit;

FIG. 9 is a perspective view illustrating a first optical unit with thelighting unit and the image forming unit;

FIG. 10 is a sectional view along A-A line in FIG. 9;

FIG. 11 is a perspective view illustrating a second optical systemincluded in a second optical unit, with the projection lens unit, thelighting unit, and the image forming unit;

FIG. 12 is a perspective view illustrating the second optical unit withthe first optical unit, the lighting unit, and the image forming unit;

FIG. 13 is a perspective view illustrating light paths from the firstoptical system to the projection plane;

FIG. 14 is a schematic view illustrating an arrangement of units in theprojector;

FIG. 15 is a view illustrating a usage example of the projectoraccording to the embodiment;

FIG. 16 is a view illustrating a usage example of a conventionalprojector;

FIG. 17 is a view illustrating a usage example of another conventionalprojector;

FIG. 18 is a perspective view illustrating the projector from aninstallation side thereof;

FIG. 19 is a perspective view illustrating a state that an access coveris removed from the apparatus;

FIG. 20 is a schematic view illustrating airflows in the projector;

FIG. 21 is a view illustrating the configuration illustrated in FIG. 20more specifically;

FIG. 22 is a section along A-A line in FIG. 21;

FIG. 23 is a section along B-B line in FIG. 21;

FIG. 24 is a section along C-C line in FIG. 21;

FIG. 25 is a section along D-D line in FIG. 21;

FIG. 26 is a section along E-E line in FIG. 21;

FIG. 27 is a perspective view illustrating a board to be mounted on themain body;

FIG. 28 is a perspective view illustrating a state that an exhaust fanand a light source housing are removed from the state illustrated inFIG. 27;

FIGS. 29A and 29B are perspective views illustrating a power sourceunit;

FIGS. 30A and 30B are perspective views illustrating a ballast boardunit;

FIG. 31 is a perspective view illustrating a state that the ballastboard unit is removed from the main body; and

FIG. 32 is a block diagram illustrating power supply.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of a projector as an image projection apparatusaccording to the present invention will be described with reference tothe accompanying drawings. FIG. 1 perspectively illustrates a projector1 and a projection plane 101 such as a screen according to anembodiment. Incidentally, in the following explanation, a normal linedirection of the projection plane 101 is referred to as X direction, ashort axis direction (vertical direction) of the projection plane 101 isreferred to as Y direction, and a long axis direction (horizontaldirection) of the projection plane 101 is referred to as Z direction.

As illustrated in FIG. 1, a transmissive glass 51 from which aprojection image P is emitted is disposed at a top surface of theprojector 1. The projection image P emitted from the transmissive glass51 is projected on the projection plane 101 such as a screen.

Furthermore, at the top surface of the projector 1, an operating part 83by which a user operates the projector 1 is disposed. At a side surfaceof the projector, a focus lever 33 for a focus adjustment is disposed.

FIG. 2 illustrates light paths from the projector 1 to the projectionplane 101.

The projector 1 is provided with (i) a light source unit including alight source and (ii) an image forming part A to form an image by usinga light from the light source. The image forming part A includes (i) animage forming unit 10 provided with a DMD (Digital Mirror Device) 12 asan image forming element and (ii) a lighting unit 20 for reflecting thelight from the light source to the DMD 12 so that an optical image isgenerated. The projector 1 is also provided with a projection opticalsystem B to project the image on the projection plane 101. Theprojection optical system B has at least one transmissive refractingoptical system and includes (i) a first optical unit 30 provided with afirst optical system 70 which is a coaxial optical system having apositive power and (ii) a second optical unit 40 provided with areflecting mirror 41 and a concave mirror 42 having a positive power.

The DMD 12 is irradiated with the light from the light source by thelighting unit 20. The light irradiated by the lighting unit 20 ismodulated to form the image. The optical image formed by the DMD 12 isprojected on the projection plane 101 through the first optical system70 in the first optical unit 30, and the reflecting mirror 41 and theconcave mirror 42 in the second optical unit 40.

FIG. 3 schematically and perspectively illustrates an internal structureof the projector 1.

As illustrated in FIG. 3, the image forming unit 10, the lighting unit20, the first optical unit 30, the second optical unit 40 are aligned inY direction in the figure among directions parallel to the projectionplane and an image plane of the projection image. The light source unit60 is disposed at a right side in the figure of the lighting unit 20.

Incidentally, in FIG. 3, reference numerals 32 a 1 and 32 a 2 refer tolegs of a lens holder 32 of the first optical unit 30, and referencenumeral 262 refers to a screw clamp portion for screwing (fixing byscrew) the image forming unit 10 to the lighting unit 20.

Next, each unit structure will be described.

First, the light source unit 60 will be described.

FIG. 4 schematically and perspectively illustrates the light source unit60.

The light source unit 60 includes a light source bracket 62. A lightsource 61 such as a halogen lamp, a metal halide lamp and a highpressure mercury lamp is mounted on the light source bracket 62. Thelight source bracket 62 is provided with a connector portion 62 a forconnecting with a power source side connector connected to a powersource unit 80 (see FIG. 14).

A holder 64, which holds a reflector and the like, is screwed to theupper side of the light source bracket 62 on a light emitting side ofthe light source 61. The holder 64 has an emitting window 63 at anopposite side to a side where the light source 61 is disposed. The lightemitted from the light source 61 is collected to the emitting window 63by the reflector 67, which is held by the holder 64, and emitted fromthe emitting window 63.

Light source positioning portions 64 a 1 to 64 a 3 are disposed at a topside and at X direction both ends of a bottom side of the holder 64, forpositioning the light source unit 60 relative to a lighting bracket 26(see FIG. 6) of the lighting unit 20. The light source positioningportion 64 a 3 disposed at the top side of the holder 64 is a protrusionor has a protrusion-like structure. The light source positioningportions 64 a 1 and 64 a 2 disposed at both ends of the bottom side ofthe holder 64 are holes or have hole-like structures.

At a side surface of the holder 64, a light source air inlet 64 b isdisposed for allowing an incoming flow of the air to cool down the lightsource 61. At a top surface of the holder 64, a light source air outlet64 c is disposed for allowing an outgoing flow of the air heated by thelight source 61.

The light source bracket 62 is provided with an airflow path 65 forallowing an incoming flow of the air taken from an air intake blower(see FIG. 21 and the like) as described later. At the air intake side(front side in the figure) of the airflow path 65, openings 65 a aredisposed for guiding a part of the airflow flowing into the airflow path65 to between the light source unit 60 and an access cover 54 (see FIG.7) which will be described later. The cooling of the light source unit60 will be described later.

A planar portion 64 d 2 on which the light source positioning protrusion64 a 3 is formed as illustrated in FIG. 4, and planar portions 64 d 1provided with the light source positioning holes 64 a 1 and 64 a 2 areabutting members for abutting against the lighting bracket when pressedby a pressing member of the access cover, as described later.

Next, the lighting unit 20 will be described.

FIG. 5 perspectively illustrates optical system components housed in thelighting unit 20, while also illustrating other units.

As illustrated in FIG. 5, the lighting unit 20 includes a color wheel21, a light tunnel 22, two relay lenses 23, a cylinder mirror 24, and aconcave mirror 25, which are held by the lighting bracket 26. Thelighting bracket 26 has a housing-like portion 261 in which two relaylenses 23, the cylinder mirror 24, and the concave mirror 25 are housed.Among four lateral sides of the housing-like portion 261, only rightlateral side in the figure has a wall. Other three lateral sides areopened. At the opening of the lateral side deep in X direction in thefigure, an OFF light board 27 (see FIG. 6) is attached. At the openingof the front lateral side in X direction in the figure, a covercomponent is attached. Thereby, two relay lenses 23, the cylinder mirror24, and the concave mirror 25, which are housed in the housing-likeportion 261 of the lighting bracket 26, are surrounded by the lightingbracket 26, the OFF light board 27 (see FIG. 6), and the covercomponent.

At a bottom surface of the housing-like portion 261 of the lightingbracket 26, a lighting through hole 26 d is formed for exposing the DMD12.

The lighting bracket 26 has three legs 29. These legs 29 abut on a basecomponent 53 (see FIG. 19) of the projector 1 to support weights of thefirst optical unit 30 and the second optical unit 40 which are stackedand fixed on the lighting bracket 26. These legs 29 disposed as suchform a space for allowing an incoming flow of ambient air toward a heatsink 13 (see FIG. 6) as a cooling unit to cool down the DMD 12 of theimage forming unit 10, which will be described later.

Incidentally, in FIG. 5, reference numerals 32 a 3 and 32 a 4 refer tolegs of the lens holder 32 of the first optical unit 30, and a referencenumeral 45 a 3 refer to a screw fix portion 45 a 3 of the second opticalunit 40.

FIG. 6 is a perspective view from a direction indicated by an arrow A inFIG. 5 and illustrates the lighting unit 20, the projection lens unit31, and the image forming unit 10.

At an upper side of the housing-like portion 261 of the lighting bracket26, an upper plate 26 b is disposed orthogonally to Y direction in thefigure. At four corner of this upper plate 26 b, through holes forletting through screws for screwing the first optical unit 30 aredisposed (in FIG. 6, through holes 26 c 1 and 26 c 2 are illustrated).Positioning holes 26 e 1 and 26 e 2 for positioning the first opticalunit 30 to the lighting unit 20 are disposed adjacent to the throughholes 26 c 1 and 26 c 2 located at the front side in X direction in thefigure. Among two positioning holes disposed at the front side in Xdirection in the figure, the positioning hole 26 e 1 at a side of whichthe color wheel 21 is disposed is a main reference for the positioningand has a round hole shape. The positioning hole 26 e 2 at an oppositeside of the color wheel 21 installation side is a sub reference for thepositioning, and has an elongate hole extending in Z direction. Aperiphery of through hole 26 c 1 and a periphery of through hole 26 c 2are protruded from a surface of the upper plate 26 b of the lightingbracket 26. These protruded peripheries functions as positioningprotrusions 26 f for positioning the first optical unit 30 in Ydirection. If the positioning accuracy in Y direction should be improvedwithout employing the positioning protrusions 26 f, it is required toimprove an entire flatness of the upper plate 26 b of the lightingbracket 26. This raises the cost. On the other hand, by employing thepositioning protrusions 26 f, it is enough to improve the flatness ofthe positioning protrusions 26 f only. Thereby, the positioning accuracyin Y direction can be improved, while saving the cost.

A light shielding plate 262 is disposed at the opening of the upperplate 26 b of the lighting bracket 26. A lower portion of the projectionlens unit 31 engages with the light shielding plate 262, so that thelight from the upper side to inside of the housing-like portion 261 isshielded.

A space between the through hole 26 c 1 and the through hole 26 c 2 ofthe lighting bracket 26 is cut off so as not to be an obstacle when thesecond optical unit 40 is screwed to the first optical unit 30, whichwill be described later.

At the color wheel side (the front side in Z direction in the figure) ofthe lighting bracket 26, a cylinder-like light source positioning jointportion 26 a 3 is disposed. The cylinder-like light source positioningjoint portion 26 a 3 has a vertical through hole into which theprotrusion-like light source positioning portion 64 a 3 (see FIG. 4)formed on the upper surface of the holder 64 of the light source unit 60fits or engages. Below the light source positioning joint portion 26 a3, two protrusion-like light source positioning joint portions 26 a 1and 26 a 2 are disposed, which engage with two hole-like light sourcepositioning portion 64 a 1 and 64 a 2 formed on the light source bracket62 side of the holder 64. By engaging three light source positioningportions 64 a 1 to 64 a 3 of the holder 64 with three light sourcepositioning joint portions 26 a 1 to 26 a 3 formed on the lightningbracket 26 of the lighting unit 20, the light unit 60 is positioned andfixed to the lighting unit 20 (see FIG. 3).

To the lighting bracket 26, a lighting cover 28 for covering the colorwheel 21 and the light tunnel 22 is attached.

FIG. 7 is for explaining the light path L of the light in the lightingunit 20.

The color wheel 21 has a disc-like shape, and is fixed to a motor shaftof a color motor 21 a. The color wheel 21 is provided with filters suchas red (R) filer, green (G) filter, and blue (B) filter in a rotatingdirection. The light collected by the reflector disposed on the holder64 of the light source unit 60 reaches a peripheral portion of the colorwheel 21 through the emitting window 63. The light reached theperipheral portion of the color wheel 21 is split into R, G and B in atime divided manner by the rotation of the color wheel 21.

The light split by the color wheel 21 enters the light tunnel. 22. Thelight tunnel 22 has a square cylinder shape. The inner peripheralsurface of the light tunnel 22 is a mirror surface. The light enteredthe light tunnel 22 is formed into a uniform surface light source whilereflected multiple times on the inner surface of the light tunnel 22,and emitted to the relay lenses 23.

The light passed through the light tunnel 22 transmits two relay lenses23, and is reflected by the cylinder mirror 24 and the concave mirror25, and is collected on an image forming surface of the DMD 12 where animage is formed.

Next, the image forming unit 10 will be described.

FIG. 8 perspectively illustrates the image forming unit 10.

As illustrated in FIG. 8, the image forming unit 10 is provided with aDMD board 11 to which the DMD 12 is attached. The DMD 12 is attached toa socket 11 a formed on the DMD board 11 so that the image formingsurface in which micromirrors are arranged in an array (grid) facesupward. The DMD board 11 is provided with a drive circuit and the likefor driving the DMD mirror. A heat sink 13 as a cooling unit to cooldown the DMD 12 is fixed to a back side (an opposite side of the socket11 a formed side) of the DMD board 1. A portion of the DMD board 11 towhich the DMD 12 is attached is opened through. The heat sink 13 isprovided with a protrusion portion 13 a (see FIG. 7) which engages withthe through hole of the DMD board 11. A leading head of the protrusionportion 13 a is flattened. This protrusion portion 13 a is inserted intothe through hole of the DMD board 11, so that the flat portion at theleading edge of the protrusion portion 13 a abuts on the back surface(the opposite surface of the image forming surface) of the DMD 12. It ispossible to improve the adhesiveness and thermal conductivity betweenthe flat portion of the protrusion portion 13 a and the back surface ofthe DMD 12 by applying an elastically deformable heat transfer sheet tothe flat portion and/or a portion of the back surface of the DMD 12 onwhich the heat sink 13 abuts.

By a fix unit 14, the heat sink 13 is pressured and fixed to the DMDboard 11 at a side opposite to a side at which the socket 11 a isformed. The fix unit 14 includes plate-like fix portions 14 a. One ofthe plate-like portions 14 a faces the back surface of the DMD board 11at a right side in the figure. The other plate-like portion 14 a facesthe back surface of the

DMD board 11 at a left side in the figure. Pressure portions 14 b aredisposed near both ends in X direction of each fix portion 14 a so thatright and left fix portions 14 a are connected.

The heat sink 13 is pressured and fixed by the fix unit 14 to the DMDboard 11 at a side opposite to a side at which the socket 11 a isformed, when the image forming unit 10 is screwed to the lightingbracket 26 (see FIG. 6).

Now, the fix procedure of the image forming unit 10 to the lightingbracket 26 will be described. First, the image forming unit 10 ispositioned to the lighting bracket 26 so that the DMD 12 faces theopening of the lighting through hole 26 d formed at the lower surface ofthe lighting bracket 26 of the lighting unit 20 as illustrated in FIG.5. Next, screws are inserted from the lower side in the figure so thateach screw goes through the through hole of the fix portion 14 a and thethrough hole 15 of the DMD board 11. Each screw is screwed into a screwhole formed at the lower side of the screw portion 262 (see FIG. 3)formed on the lighting bracket 26. As the screw is screwed into thescrew portion 262 of the lighting bracket 26, the pressure portion 14 bpresses the heat sink 13 toward the DMD board 11. Thereby, the heat sink13 is pressed and fixed by the fix unit 14 to a surface of the DMD board11 opposite to a surface on which the socket 11 a is formed.

Thus, the image forming unit 10 is fixed to the lighting unit 26. Asillustrated in FIG. 5, three legs 29 also support the weight of theimage forming unit 10.

In the image forming surface of the DMD 12, a plurality of movablemicromirrors are arranged in an array (grid). Each of micromirrors cantilt its mirror surface by a predetermined angle around a torsion axis.Thus, each of micromirrors can take ON position or OFF position. If amicromirror is at ON position, the light from the light source 61 isreflected to the first optical system 70 (see FIG. 2), as illustrated byan arrow L2 in FIG. 7. If a micromirror is at OFF position, the lightfrom the light source 61 is reflected to the OFF light plate 27 held atthe lateral side of the lighting bracket 26 as illustrated in FIG. 6(see an arrow L1 in FIG. 7). Therefore, by driving each mirrorindependently, it is possible to control the light projection for eachpixel of the image data and thus form the image.

The light reflected toward the OFF light plate 27 is absorbed as heatand then cooled by an ambient air flow.

Next, the first optical unit 30 will be described.

FIG. 9 perspectively illustrates the first optical unit 30 with thelighting unit 20 and the image forming unit 10.

As illustrated in FIG. 9, the first optical unit 30 is disposed abovethe lighting unit 20. The first optical unit 30 is provided with theprojection lens unit 31 holding the first optical system 70 (see FIG. 2)including a plurality of lenses, and the lens holder 32 for holding thisprojection lens unit 31.

The lens holder 32 has four legs 32 a 1 to 32 a 4 extending downward (inFIG. 9, only legs 32 a 2 and 32 a 3 are illustrated. The leg 32 a 1 isillustrated in FIG. 3, and the leg 32 a 4 is illustrated in FIG. 5). Ascrew hole is formed at a bottom surface of each of legs 32 a 1 to 32 a4, for screwing each leg to the lighting bracket 26.

The projection lens unit 31 is provided with a focus gear 36 with whichan idle gear 35 engages. The idle gear 35 engages with a lever gear 34.A focus lever 33 is fixed to a rotational axis of the lever gear 34. Theleading edge of the focus lever 33 is exposed from the main body asillustrated in FIG. 1.

When the focus lever 33 is moved, the focus gear 36 is rotated via thelever gear 34 and the idle gear 35. When the focus gear 36 is rotated,the plurality of lenses composing the first optical system 70 in theprojection lens unit 31 is moved toward predetermined directions so thata focus of the projection image is adjusted.

The lens holder 32 has four screw through holes 32 c 1 to 32 c 4 throughwhich screws 48 penetrate for screwing the second optical unit 40 to thefirst optical unit 30 (in FIG. 9, three screw through holes 32 c 1 to 32c 3 are illustrated. Each of three screw through holes is illustrated ina state that a screw 48 is penetrated. The edge of the screw 48 isviewed in the figure.) Around each of screw through holes 32 c 1 to 32 c4, the second optical unit positioning protrusions 32 d 1 to 32 d 4protruded from the surface of the lens holder 32 are formed (in FIGS. 9,32 d 1 to 32 d 3 are illustrated).

FIG. 10 is a sectional view along A-A line in FIG. 9.

As illustrated in FIG. 10, legs 32 a 1 and 32 a 2 are provided withpositioning joint protrusions 32 b 1 and 32 b 2, respectively. Thepositioning joint protrusion 32 b 1 at the right side in the figure isinserted into the round hole shaped positioning hole 26 e 1 which isformed as the main reference at the upper plate 26 b of the lightingbracket 26. The positioning joint protrusion 32 b 2 at the left side inthe figure is inserted into the elongate hole shaped positioning hole 26e 2 which is formed as the sub reference on the upper plate 26 b of thelighting bracket 26. Thus, the positioning in Z direction and Xdirection is done. Screws 37 are inserted into through holes 26 c 1 to26 c 4 formed at the upper plate 26 b of the lighting bracket 26, sothat screws 37 are screwed into screw holes formed on each of legs 32 a1 to 32 a 4 of the lens holder 32, and the first optical unit 70 ispositioned and fixed to the lighting unit 20.

The upper portion of the projection lens unit 31 above the lens holder32 is covered by a mirror holder 45 (see FIG. 12) of the second opticalunit, which will be described later. As illustrated in FIG. 3, below thelens holder 32 of the projection lens unit 31, a portion of theprojection lens unit 31 between the lens holder 32 and the upper plate26 b of the lighting bracket 26 of the lighting unit 20 is exposed.However, the light cannot enter from this exposed portion to the lightpath of the image, since the projection lens unit 31 engages with thelens holder 32.

Next, the second optical unit 40 will be described.

FIG. 11 perspectively illustrates the second optical system included inthe second optical unit 40, while also illustrating the projection lensunit 31, the lighting unit 20 and the image forming unit 10.

As illustrated in FIG. 11, the second optical unit 40 is provided withthe reflecting mirror 41 and the concavely curved mirror 42 composingthe second optical system. A reflecting surface of the curved mirror 42may be a spherical surface, a rotationally symmetric aspheric surface, afree curved surface or the like.

FIG. 12 perspectively illustrates the second optical unit 40 with thefirst optical unit 30, the lighting unit 20, and the image forming unit10.

As illustrated in FIG. 12, the second optical unit 40 is provided with atransmissive glass 51 for transmitting the light image reflected fromthe curved mirror 42 and for protecting optical components in theapparatus from dust.

The second optical unit 40 includes a mirror bracket 43 for holding thereflecting mirror 41 and the transmissive glass 51, a free mirrorbracket 44 for holding the curved mirror 42, and the mirror holder 45 towhich the mirror bracket 43 and the free mirror bracket 44 are attached.

The mirror holder 45 has a box shape. Specifically, it has a U shapewhen viewed from the upper side in which the upper side, the bottomside, and the depth side of X direction in the figure of the box areopened. Edge portions of the upper opening of the mirror holder 45extend from the front side to the depth side in X direction at the frontside and the depth side in Z direction. Each of these edge portions hasan inclined portion and a parallel portion. The inclined portioninclines so that it is raised as it goes to the depth in X direction inthe figure. The parallel portion is parallel to X direction in thefigure. The inclined portion is on the front side of the parallelportion in X direction. An edge portion of the upper opening of themirror holder 45 extending in Z direction at the front side in Xdirection in the figure is parallel to Z direction in the figure.

The mirror bracket 43 is attached to the upper part of the mirror holder45. The mirror bracket 43 has an inclined surface 43 a and a parallelsurface 43 b. The inclined surface 43 a abuts on the inclined portion ofthe upper opening edges of the mirror holder 35, and inclines so that itis raised as it goes to the depth in X direction in the figure. Theparallel surface 43 b, which is parallel to X direction, abuts on theparallel portion of the upper opening edges of the mirror holder 45. Theinclined surface 43 a and the parallel surface 43 b have openings,respectively. In these openings, the reflecting mirror 41 is held sothat the opening of the inclined surface 43 a is closed, and thetransmissive glass 51 is held so that the opening of the parallelsurface 43 b is closed.

The reflecting mirror 41 is positioned and fixed to the inclined surface43 a of the mirror bracket 43 by pressing Z direction both ends of thereflecting mirror 41 against the inclined surface 43 a of the mirrorbracket 43 by a flat spring-like mirror pressing members 46. One Zdirection end of the reflecting mirror 41 is fixed by two mirrorpressing members 46, and the other Z direction end of the reflectingmirror 41 is fixed by one mirror pressing member 46.

The transmissive glass 51 is positioned and fixed to the mirror bracket43 by pressing Z direction both ends of the transmissive glass 51against the parallel surface 43 b of the mirror bracket 43 by a flatspring-like glass pressing members 47. Each Z direction end of thetransmissive glass 51 is fixed by one glass pressing member 47,respectively.

The free mirror bracket 44 for holding the curved mirror 42 has arms 44a at Z direction both sides thereof Each of arms 44 a declines so thatit is lowered as it goes to the front side from the depth side in Xdirection in the figure. The free mirror bracket 44 also has aconnecting portion 44 b for connecting two arms 44 a at an upper side oftwo arms 44 a. With regard to this free mirror bracket 44, arms 44 a areattached to the mirror holder 45 so that the curved mirror 42 covers theX direction depth side opening of the mirror holder 45.

The curved mirror 42 is fixed in such a manner that a substantialcentral portion of the transmissive glass side end of the curved mirror42 is pressed against the connecting portion 44 b of the free mirrorbracket 44 by a plate spring-like free mirror pressing member 49, and Zdirection both ends of the curved mirror 42 on the first optical systemside are fixed to arms 44 a of the free mirror bracket 44 by screws.

The second optical unit 40 is stacked on and fixed to the lens holder 32of the first optical unit 30. Specifically, an under surface 451 isformed under the mirror holder 45 which faces the upper surface of thelens holder 32. The under surface 451 has four cylindrical screw joints45 a 1 to 45 a 4 (only 45 a 1 and 45 a 2 are illustrated in FIGS. 13,and 45 a 3 is illustrated in FIG. 6) formed for screwing the secondoptical unit 40 to the first optical unit 30. The second optical unit 40is fixed to the first optical unit 30 in such a manner that screws 48are penetrated through screw holes 32 c 1 to 32 c 4 formed on the lensholder 32 of the first optical unit 30, and then screwed and fastenedinto screw joints 45 a 1 to 45 a 4. At this time, the under surface ofthe mirror holder 45 of the second optical unit 40 abuts on the secondoptical unit positioning protrusions 32 d 1 to 32 d 4 of the lens holder32, so that the second optical unit 40 is positioned in Y direction andfixed.

When the second optical unit 40 is stacked on and fixed to the lensholder 32 of the first optical unit 30, the upper portion of theprojection lens unit 31 above the lens holder 32 as illustrated in FIG.9 is housed in the mirror holder 45 of the second optical unit 40. Whenthe second optical unit 40 is stacked on and fixed to the lens holder 32of the first optical unit 30, a gap is made between the curved mirror 42and the lens holder 32. The idle gear 35 (see FIG. 9) is inserted intothe gap.

FIG. 13 perspectively illustrates the light paths from the first opticalsystem 70 to the projection plane 101 (screen).

The light beam passed through the projection lens unit 31 composing thefirst optical system 70 forms an intermediate image conjugate to theimage formed on the DMD 12 between the reflecting mirror 41 and thecurved mirror 42. This intermediate image is formed as a curved mirrorimage between the reflecting mirror 41 and the curved mirror 42. Next,the optical image enters the concavely curved mirror 42, so that theintermediate image becomes a “further enlarged image” to be projectedand formed on the projection plane 101 by the curved mirror 42.

Thus, owing to the structure in which the projection optical system iscomposed of the first optical system 70 and the second optical system,the intermediate image is formed between the first optical system 70 andthe curved mirror 42 of the second optical system, and the intermediateimage is enlarged and projected by the curved mirror 42, the projectiondistance can be shortened. Thus, the projectors can be used in smallrooms.

As illustrated in FIG. 13, the first optical unit 30 and the secondoptical unit 40 are stacked on and fixed to the lighting bracket 26.Furthermore, the image forming unit 10 is also fixed. Therefore, legs 29of the lighting bracket 26 are fixed to the base component 53 so thatthe legs 29 support weights of the first optical unit 30, the secondoptical unit 40 and the image forming unit 10.

FIG. 14 schematically illustrates an arrangement of units in theprojector.

As illustrated in FIG. 14, the image forming unit 10, the lighting unit20, the first optical unit 30 and the second optical unit 40 arearranged in a stacked manner in Y direction which is a short axisdirection of the projection plane. Relative to stacked units of theimage forming unit 10, the lighting unit 20, the first optical unit 30and the second optical unit 40, the light source unit 60 is disposed inZ direction which is a long axis direction of the projection plane.Thus, in the present embodiment, the image forming unit 10, the lightingunit 20, the first optical unit 30, the second optical unit 40 and thelight source unit 60 are arranged in Y direction and Z direction whichare parallel to the projection plane 101. More specifically, the imageforming unit 10 and the lighting unit 20 form the image forming part A,while the first optical unit 30 and the second optical unit 40 form theprojection optical part B. The light source unit 60 is connected to theimage forming part A in a direction perpendicular to a direction inwhich the image forming part A and the projection optical part B arestacked. The image forming part A and the light source unit 60 arearranged along the same line parallel to the base component 53. Theimage forming part A and the projection optical part B are arrangedalong the same line perpendicular to the base component 53, in the orderof the image forming part A and the projection optical part B from thebase component 53.

In the present embodiment, above the light source unit 60, a powersource unit 80 is stacked for supplying an electrical power to the lightsource 61 and the DMD 12. The light source unit 60, the power sourceunit 80, the image forming part A and the projection optical part B arehoused in a case of the projector 1 made of an outer cover (see FIG.18), which will be described later, covering the upper surface of theprojector, the base component 53 and the surrounding of the projector 1.

FIG. 15 illustrates a usage example of the projector 1 according to thepresent embodiment. FIG. 16 and FIG. 17 illustrate usage examples ofconventional projectors 1A and 1B.

As illustrated in FIG. 15 to FIG. 17, the projector is used in such amanner that the projector is put on a table 100 and an image isprojected on the projection plane 101 such as a white board, when usedin a meeting room or the like for example.

As illustrated in FIG. 16, in the conventional projector 1A, a DMD 12(image forming element), a lighting unit 20, a first optical system 70,and a second optical system (curved mirror 42) are arranged in series ina direction orthogonal to a plane of a projection image projected on aprojection plane 101. Therefore, the projector 1A is elongated in thedirection (X direction) orthogonal to the projection plane of theprojector 1A. Thus, the projector 1A occupies a space in the directionorthogonal to the projection plane 101. Desks and chairs used by viewersof the image projected on the projection screen 101 are generallyarranged in the direction orthogonal to the projection plane. Thus, ifthe projector occupies the space in the direction orthogonal to theprojection plane, the layout space allowed for desks and chairs islimited. It is inconvenient.

In the projector 1B illustrated in FIG. 17, a DMD 12 (image formingelement), a lighting unit 20 and a first optical system 70 are arrangedin series parallel to a plane of a projection image projected on aprojection plane 101. Therefore, in comparison with the projector 1Aillustrated in FIG. 16, a length in a direction orthogonal to theprojection plane 101 can be shortened. However, in the projector 1Billustrated in FIG. 17, relative to the lighting unit 20, a light source61 is arranged in the direction orthogonal to the plane of theprojection image. Therefore, the length in the direction orthogonal tothe projection plane 101 of the projector cannot be sufficientlyshortened.

On the other hand, in the projector 1 according to the presentembodiment illustrated in FIG. 15, the image forming part A composed ofthe image forming unit 10 and the lighting unit 20 and the projectionoptical part B composed of the first optical unit 30 and the reflectingmirror 41 are arranged in series along Y direction in the figure amongdirections parallel to the projection plane 101 and the image plane ofthe projection image projected on the projection plane 101. Furthermore,the light source unit 60 and the lighting unit 20 are arranged in seriesalong Z direction in the figure among directions parallel to the planeof the projection image projected on the projection plane 101. Namely,the projector 1 according to the present embodiment has a configurationin which the light source unit 60, the image forming unit 10, thelighting unit 20, the first optical unit 30, and the reflecting mirror41 are arranged in directions (Z and Y directions in the figure)parallel to the plane of the projection image projected on theprojection plane 101. Each of the light source unit 60, the imageforming unit 10, the lighting unit 20, the first optical unit 30, andthe reflecting mirror 41 is arranged so as to intersect a plane parallelto the projection plane and the image plane of the projection image.Thus, since the light source unit 60, the image forming unit 10, thelighting unit 20, the first optical unit 30, and the reflecting mirror41 are arranged in directions (Z and Y directions in the figure)parallel to the plane of the projection image projected on theprojection plane 101, a length in a direction (X direction in thefigure) orthogonal to the projection plane 101 can be shortened asillustrated in FIG. 15, in comparison with projectors illustrated inFIG. 16 and FIG. 17. Thereby, the projector 1 cannot be an obstacle forthe layout of desks and chairs in view of spaces. Thus, it is possibleto provide the convenient projector 1.

In the present embodiment, as illustrated in FIG. 14, above the lightsource unit 60, the power source unit 80 for supplying the electricalpower to the light source 61 and the DMD 12 is disposed in a stackedmanner. Thereby, a length of the projector 1 in Z direction is alsoshortened.

In the present embodiment, the second optical system is composed of thereflecting mirror 41 and the curved mirror 42. However, the secondoptical system may be composed only of the curved mirror 42. Thereflecting mirror may be a flat mirror, a mirror having a positiverefractive power, or a mirror having a negative refractive power. In thepresent embodiment, the concave mirror is used as the curved mirror 42.However, a convex mirror may be used. In this case, the first opticalsystem 70 is configured so that an intermediate image is not formedbetween the first optical system 70 and the curved mirror 42.

The light source 61 is to be replaced periodically, since its life timeends after use over time. For this purpose, in the present embodiment,the light source unit 60 is arranged detachably from and attachably tothe main body.

FIG. 18 perspectively illustrates an installation side of the projector1. As illustrated in FIG. 18, the base component 53 constituting thebottom surface of the projector 1 is provided with an access cover 54(openalble/closenable cover). The access cover 54 is provided with arotating operating member 54 a. The rotating operating member 54 a canbe rotated to release the lock between the access cover 54 and the mainbody, so that the access cover can be removed from the main body.Electrical power air inlets 56 are disposed adjacent in X direction tothe access cover 54 of the base component 53.

As illustrated in FIG. 18, in one of XY planes of an outer cover 59 ofthe projector 1, an air inlet 84, and an external input portion 88 fromwhich the image data or the like is input from an external device suchas a PC are disposed.

FIG. 19 perspectively illustrates a state that the access cover 54 isremoved from the main body.

As illustrated in FIG. 19, if the access cover 54 is removed, a side ofthe light source bracket 62 opposite to a side on which the light source61 is mounted in the light source unit 60 is exposed. A handle portion66 is rotatably attached to the light source bracket 62 so that thehandle portion 66 can rotate around a dotted line 01 in the figurerelative to the light source bracket 62.

When the light source unit 60 is to be removed from the main body, thehandle portion 66 is rotated, pinched and pulled toward the nearer sidein the figure, so that the light source unit 60 is removed from theopening of the main body. When the light source unit 60 is to be mountedto the main body, the light source unit 60 is inserted from the openingof the main body. As the light source unit 60 is inserted into the mainbody, the connecting portion 62 a as illustrated in FIG. 4 connects withthe power source side connector of the main body. Three light sourcepositioning portions 64 a 1 to 64 a 3 of the holder 64 as illustrated inFIG. 4 engage with three light source positioning joint portions 26 a 1to 26 a 3 formed on the lighting bracket 26 of the lighting unit 20 asillustrated in FIG. 6, so that the light source unit 60 is positioned tothe main body. Thus, the mounting of the light source unit 60 iscompleted. Then, the access cover 54 is attached to the base component53. In the present embodiment, the light source unit 60 has the handleportion 66. However, an airflow path 65 protruded toward the accesscover 54 as illustrated in FIG. 19 may be used as the handle portion.

The base component 53 has three legs 55. By rotating these legs 55, theprotruded extent of legs 55 from the base component 53 can be changed,and the adjustment in the height direction (Y direction) can be done.

As illustrated in FIG. 19, in the other XY plane of the outer cover 59,an exhaust outlet 85 is disposed.

FIG. 20 is a view illustrating air flows in the projector 1 according tothe present embodiment. In FIG. 20, the projector 1 is viewed from thedirection (X direction) orthogonal to the projection plane 101. In FIG.21, schematically illustrated components in FIG. 20 are specificallyillustrated carrying the same reference numerals. In FIG. 20 and FIG.21, arrows indicate directions to which air flows. FIG. 22 is a crosssection along A-A line of FIG. 21. FIG. 23 is a cross section along B-Bline of FIG. 21. FIG. 24 is a cross section along C-C line of FIG. 21.FIG. 25 is a cross section along D-D line of FIG. 21. FIG. 26 is a crosssection along E-E line of FIG. 21.

As illustrated in FIG. 20, at one side (left side in the figure) of theprojector 1, the air inlet 84 is formed for taking an ambient air intothe projector 1. At another side (right side in the figure) of theprojector 1, the exhaust outlet 85 is formed for discharging the airinside of the projector 1. An exhaust fan 86 is disposed so as to facethe exhaust outlet 86.

The exhaust outlet 85 and a part of the air inlet 84 are located at alevel between the light source unit 60 and the operating part 83, whenthe projector 1 is viewed from the direction (X direction) orthogonal tothe projection plane 101. Furthermore, a flow path is formed between theback surface of the curved mirror 42 and the outer cover 59 facing theback surface of the curved mirror 42 for allowing the airflowtherethrough. Thereby, the ambient air taken from the air inlet 84 flowsto ZY plane of the mirror holder 45 and the back surface of the curvedmirror 42 of the second optical unit 40 as illustrated in FIG. 12. Alongthe mirror holder 45 and the back surface of the curved mirror 42, theair flows toward the exhaust outlet 85 (see FIG. 22, FIG. 24, and FIG.26). The curved mirror 42 is a concave mirror having a positive power asmentioned above. The back surface of the curved mirror 42 has a convexshape almost along the front side shape thereof. The power source unit80 disposed above the light source unit 60 has an almost U shape withoutonly an edge on the light source unit side 60 when viewed from Zdirection in the figure (see FIG. 23). The air taken from the air inlet84 flows along the mirror holder 45 and the back surface of the curvedmirror 42 toward the exhaust outlet 84, so that the air flows into aspace surrounded by the power source unit 80 on three sides of the spaceexcepting the light source unit 60 side and is then discharged from theexhaust outlet 85.

Thus, the exhaust outlet and the part of the air inlet are located at alevel between the light source unit 60 and the operating part 83 whenthe projector 1 is viewed from the direction (X direction) orthogonal tothe projection plane 101. Thereby, there is generated the airflow whichflows between the light source unit 60 and the operating part 83 and isthen discharged from the exhaust outlet 85.

A light source blower 95 (see FIG. 25) is disposed at a positionallowing for suctioning the air around the color motor 21 a (see FIG. 5)to drive and rotate the color wheel 21 of the lighting unit 20. Thereby,the color motor 21 a and the light tunnel 22 can be cooled by theairflow generated by the air suction of the light source blower 95.

The air suctioned by the light source blower 95 flows to the lightsource air inlet 64 b (see FIG. 4) of the holder 64 through the lightsource duct 96. A part of the air flows into the light source duct 96flows from an opening 96 a, which is formed on the light source duct 96on a side facing the outer cover 59 (see FIG. 19), to between the lightsource housing 97 and the outer cover 59.

The air flowing from the opening 96 a of the light source duct 96 tobetween the light source housing 97 and the outer cover 59 cools downthe light source housing 97 and the outer cover 59, and is thendischarged from the exhaust outlet 85 by the exhaust fan 86.

The air flowing to the light source air inlet 64 b flows into the lightsource 61. After cooling the light source 61, the air is discharged fromthe light source air outlet 64 c formed on the upper surface of theholder 64. The air discharged from the light source air outlet 64 cflows toward the exhaust outlet 85 along a fluid guide 87 from theopening on the top surface of the light source housing 97 as illustratedin FIG. 21. Then, the air is mixed with the low temperature air whichflows along the outside of the second optical unit 40 and flows into thespace surrounded by the power source unit 80. Then, the air isdischarged from the exhaust outlet 85 by the exhaust fan 86. Thus, thehigh temperature air discharged from the light source air outlet 64 c ismixed with the ambient air and then discharged to the ambient. Thereby,it is possible to prevent the temperature rise of the air dischargedfrom the exhaust outlet 85. Incidentally, the fluid guide 87 is notnecessarily required. Even if the fluid guide 87 is not equipped, thehigh temperature air exhausted from the light source exhaust outlet 64 cis exhausted from the exhaust outlet 85 by the airflow toward theexhaust outlet 85 from the air inlet 84 via the back surface of thecurved mirror 42 in a space surrounded by a main PFC power source board80 a and a sub PFC power source board 80 b, which will be describedlater. On the other hand, employing the fluid guide 87 can prevent thehigh temperature air, which is exhausted from the light source exhaustoutlet 64 c, from flowing directly to near the main PFC power sourceboard 80 a and the sub PFC power source board 80 b. However, if it isattempted to avoid all the high temperature air, which is exhausted fromthe light source exhaust outlet 64 c, from the main PFC power sourceboard 80 a and the sub PFC power source board 80 b, all the hightemperature air is not mixed with the air passed through the backsurface of the curved mirror 42. Thus, all the high temperature air isexhausted from the exhaust outlet 85 without cooling or lowering itstemperature. Therefore, the exhaust outlet 85 becomes hot. Therefore, itis better for the user that at least a part of the air exhausted fromthe light source exhaust outlet 64 c and passed through the fluid guide87 flows through the space surrounded by the main PFC power source board80 a and the sub PFC power source board 80 b. That is because the air iscertainly mixed with the air flowing from the air inlet 84 to theexhaust outlet 85 via the back surface of the curved mirror 42.

The operating part 83 operated by the user is preferably formed on theupper surface of the apparatus for the easy operation by the user. Inthe present embodiment, however, since the transmissive glass 51 isdisposed on the upper surface of the projector 1 for the purpose ofprojecting the image on the projection plane 101, the operating part 83needs to be disposed above the light source 61 as if they overlap eachother when the projector 1 is viewed from the Y direction.

In the present embodiment, the high temperature air after cooling thelight source 61 is guided to the exhaust outlet 85 by the airflow fromthe air inlet 84 to the exhaust outlet 85 between the light source unit60 and the operating part 83. This high temperature air is preventedfrom flowing to the operating part 83. Thereby, the operating part 83 isprevented from being heated by the high temperature air after coolingthe light source 61. Furthermore, a part of the air which flows from theair inlet 84 to the exhaust outlet 85 via the outside of the secondoptical unit 40 cools the operating part 83 by flowing beneath theoperating part 83. This also contributes to the prevention of thetemperature rise of the operating part 83.

Owing to the air suction of the exhaust fan 86, the ambient air issuctioned from the power source air inlets 56 formed on the basecomponent 53 as illustrated in FIG. 19. At the X direction depth side inthe figure beyond the light source housing 97, a ballast board 3 a (seeFIG. 24 and FIG. 25) for supplying a stabilized electrical power(electrical current) to the light source 61 is disposed. The ambient airsuctioned from the power source air inlets 56 moves upward throughbetween the light source housing 97 and the ballast board 3 a. Whilethis movement, the air cools the ballast board 3 a. Then, the air flowsinto the space surrounded by the power source unit 80 disposed above theballast board. Then, the air is discharged from the exhaust outlet 85 bythe exhaust fan 86.

In the present embodiment, the fan which generates the airflow from theair inlet 84 to the exhaust outlet 85 is disposed as the exhaust fan 86at the exhaust side. Therefore, in comparison with a case that the fanis disposed at the air inlet side, an amount of air supplied to theinside of the apparatus from the air inlet 84 can be increased. If thefan is disposed near the air inlet 84, an amount of the ambient airflowing to the inside of the apparatus decreases because of the secondoptical unit 40, since the second optical unit 40 is located in adirection to which the air is directed by the fan. On the other hand, inthe case that the fan is disposed as the exhaust fan 86 near the exhaustoutlet 85, there is no object in a direction beyond the exhaust outlet85, usually. Therefore, an amount of the air exhausted by the exhaustfan 86 does not decrease. Therefore, the air is taken from the air inlet84 as much as the air exhausted by the exhaust fan 86. Consequently, anamount of the air supplied from the air inlet to the inside of theapparatus does not decrease. Therefore, it is possible to make airflowfrom the air inlet 84 to the exhaust outlet 85 with a predeterminedpressure. Thereby, the heated air raised from the light source 61 can beadvantageously directed to the exhaust outlet 85 by the airflow from theair inlet 84 to the exhaust outlet 85.

At the lower left side of the main body in the figure, a cooling unit120 is disposed for cooling the heat sink 13 of the image forming unit10 and the light source bracket 62 of the light source unit 60. Thecooling unit 120 is provided with an air intake blower 91, a verticalduct 92, and a horizontal duct 93.

The air intake blower 91 is disposed facing the air inlet 84 at thelower part of the inlet 84. The ambient air is taken from one side ofthe blower 91 facing the air inlet 84 through the air inlet 84. The airinside of the apparatus is taken from the other side of the blower 91which is opposite to the one side facing the air inlet 84. The taken airis directed to the vertical duct 92 disposed under the blower 91. Theair directed to the vertical duct 92 moves downward and is then directedto the horizontal duct 93 connected to the vertical duct 92 at the lowerpart of the duct 92.

A heat sink 13 is disposed in the horizontal duct 93. The heat sink 13is cooled by the air flowing in the horizontal duct 93. By cooling theheat sink 13, the DMD 12 can be cooled effectively. Thus, the DMD 12 canbe prevented from being heated to high temperature.

The air moved through the horizontal duct 93 flows in the airflow path65 or the openings 65 a formed in the light source bracket 62 of thelight source unit 60 as illustrated in FIG. 4. The air entered theopenings 65 a flows to between the access cover 54 and the light sourcebracket 62, so that the access cover 54 is cooled.

On the other hand, the air entered the airflow path 65 cools the lightsource bracket 62 and then flows to a part of the light source 61opposite to the emitting side of the light source 61, so that a part ofthe light source 61 opposite to the reflecting surface of the reflector67 is cooled. Thus, the reflector 67 of the light source 61 is cooled.Therefore, the air flowing through the airflow path 65 takes heat fromboth the light source bracket 62 and the light source 61. The air passedaround the reflector 67 flows through an exhaust duct 94 which directsthe air from a level (height) of the light source bracket 62 to a levelaround the lower portion of the exhaust fan 86. Then, the air combineswith the air discharged from the light source air outlet 64 c, and flowsto the exhaust outlet 85 through a fluid guide 87. The air is dischargedfrom the exhaust outlet 85 by the exhaust fan 86. On the other hand, theair which flows between the access cover 54 and the light source bracket62 through the openings 65 a moves inside of the apparatus after coolingthe access cover 54, so that the air is discharged from the exhaustoutlet 85 by the exhaust fan 86.

The light source bracket 62 is provided with the airflow path 65, sothat the light source bracket 62 is cooled and thereby the temperaturerise of the light source 61 is suppressed. Thereby, even if the amountof the air which flows into the light source 61 is decreased incomparison with the conventional amount, the light source 61 can becooled well. Thereby, it is possible to reduce the rotation speed (rpm)of the light source blower 91. Thus, a wind noise (kazekirion) of thelight source blower 95 can be reduced. Furthermore, since the rotationspeed (rpm) of the light source blower 95 can be reduced, the electricalpower for the apparatus can be saved.

FIG. 27 perspectively illustrates a board to be arranged in the mainbody.

As illustrated in FIG. 27, the projector 1 according to the presentembodiment is provided with a control board 2 as a control unit forcontrolling, for example, drive of the DMD 12, which is the imageforming element, a ballast board unit 3 including the ballast board 3 a(see FIG. 24) as an electrical power stabilizing unit for supplying astabilized electrical power (current, voltage) to the light source 61,and the power source unit 80 including a PFC power source board as anelectrical power source unit for boosting the AC voltage supplied fromthe power source cable and supplying the power to the control board 2and the ballast board 3 a.

FIG. 28 perspectively illustrates a state that the exhaust fan 86 andthe light source housing 97 are removed from the state illustrated inFIG. 27.

As illustrated in FIG. 28, the control board 2 is arranged to face theside surface (ZY plane) of the illumination unit 20 and the firstoptical unit 30. The ballast board unit 3 is arranged at a positionadjacent to the control board 2 in the Z direction (horizontaldirection), and adjacent to the light source unit 60 in the X direction(direction orthogonal to the projection image). The power source unit 80is arranged on the upper side of the light source unit 60 and theballast board unit 3. The power source unit 80 includes a thermal switch182 for shielding the supply of voltage from the power source cable whenits temperature becomes higher than or equal to a predeterminedtemperature.

FIGS. 29A and 29B are perspective views illustrating the power sourceunit 80.

As illustrated in FIGS. 29A and 29B, and FIG. 23, the PFC power sourceboard of the power source unit 80 is divided into the main PFC powersource board 80 a as a first power source board and the sub PFC powersource board 80 b as a second power source board. The main PFC powersource board 80 a is attached to a substantially L-shaped main boardholder 81, and the sub PFC power source board 80 b is attached to a subboard holder 82. The light source unit 60 and the light source 61 arearranged on a normal line of the main PFC power source board 80 a.

The main board holder 81 includes a board attaching surface 81 a towhich the main PFC power source board 80 a is attached on the lowersurface, and a cover surface 81 b extending downward from the near sideend in the X direction in the figure of the board attaching surface 81a.

The sub board holder 82 is attached to the near side end in the Xdirection in the figure of the board attaching surface 81 a so that thesub PFC power source board 80 b faces the cover surface 81 b. Thethermal switch 182 is arranged on the sub PFC power source board 80 b.As illustrated in FIG. 27, a plurality of boards configuring the powersource unit 80, specifically, the main PFC power source board 80 a andthe sub PFC power source board 80 b are attached to the main body so asto surround the air suction inlet of the exhaust fan 86 with the boardattaching surface 81 a of the main board holder 81, the cover surface 81b, and the sub board holder 82.

The main PFC power source board 80 a, the sub PFC power source board 80b, and the cover surface 81 b are arranged to form a flow path thatsurrounds the flow of air flowing towards the exhaust fan 86 by theintake of the exhaust fan 86 as the air blowing unit, that is, to formtwo surfaces of the flow path for guiding the air flowing towards theexhaust outlet 85 from different directions. The power source unit 80may be configured by three boards to become three surfaces of the flowpath. If the fluid guide 87 is arranged, the space partially surroundedby the main PFC power source board 80 a and the sub PFC power sourceboard is the flow path from the fluid guide 87 to the exhaust outlet 85.If the fluid guide 87 is not arranged, the space partially surrounded bythe main PFC power source board 80 a and the sub PFC power source board80 b is the flow path from the light source exhaust outlet 64 c to theexhaust outlet 85. It also functions as a flow path of the air flowingfrom the air inlet 84 towards the exhaust outlet 85 via the back surfaceof the curved mirror 42. More specifically, the main PFC power sourceboard 80 a and the sub PFC power source board 80 b are arranged tobecome two surfaces of a substantially quadratic column or a polygonalcolumn connecting to the surface exhausting the air of the exhaust fan86 so as to enable the movement of the air. Neither the main PFC powersource board 80 a nor the sub PFC power source board 80 b is arranged onthe surface closest to the light source unit 60 of the four surfaces ofthe substantially quadratic column so as not to inhibit the flow of airfrom the light source unit 60 towards the exhaust outlet 85. Moreover,neither the main PFC power source board 80 a nor the sub PFC powersource board 80 b is arranged on the surface closest to the exteriorcover on the opposite side of the projection surface of the surfaces ofthe substantially quadratic column, so that the flow of air flowingtowards the exhaust outlet 85 along the back surface of the curvedmirror 42 having a concave surface shape is not inhibited, and the speedof the flow of air flowing towards the exhaust outlet 85 along the backsurface of the curved mirror 42 having a concave surface shape is notaffected. Not arranging the main PFC power source board 80 a and the subPFC power source board 80 b on the surface closest to the exterior coveron the opposite side of the projection surface of the surfaces of thesubstantially quadratic column means the same as not arranging the mainPFC power source board 80 a and the sub PFC power source board 80 b onthe cover surface 81 b of the power source unit 60. The curved mirror 42is a concave mirror having a positive power, as described above, and theback surface of the concave mirror 42 has a convex shape almost alongthe concave shape of the front surface. The flow path formed by the mainPFC power source board 80 a and the sub PFC power source board 80 b isfluidically connected with the flow path (second flow path) formed bythe back surface of the curved mirror 42 and the exterior cover 59facing the back surface of the curved mirror 42. Incidentally,“fluidically connected” herein means that the air can continuously flowthrough the “fluidically connected” flow paths. Thereby, the air takenfrom the air inlet 84 at the side surface of the exterior cover 59 andflowed towards the exhaust outlet 85 along the back surface of theconcave mirror 42 is exhausted from the exhaust outlet 85 by the exhaustfan 86 through a space surrounded by the sub PFC power source board 80b, the main PFC power source board 80 a, and the cover surface 81 b.Thus, although the main PFC power source board 80 a and the sub PFCpower source board 80 b are heated by the light source unit 60 and thefluid guide 87, they are cooled by the air flowing towards the exhaustoutlet 85 along the back surface of the concave mirror 42, so that thetemperature rise of the main PFC power source board 80 a and the sub PFCpower source board 80 b can be suppressed. Moreover, the apparatus canbe downsized by arranging the power source unit 80 in a space that couldnot be conventionally used as a place to arrange the power source unit80 due to the problem of waste heat from the light source 61.

When the main PFC power source board 80 a and the sub PFC power sourceboard 80 b are aligned in the air flowing direction, the PFC powersource board arranged on the downstream side of the air flowingdirection is cooled by the air heated by the PFC power source board onthe upstream side, and thus the PFC power source board on the downstreamside is not sufficiently cooled. However, the main PFC power sourceboard 80 a and the sub PFC power source board 80 b can be cooled withlow temperature air by arranging the main PFC power source board 80 aand the sub PFC power source board 80 b so as to surround the airflowfrom the air inlet 84 toward the exhaust outlet 85. The main PFC powersource board 80 a and the sub PFC power source board 80 b, that is, theentire PFC power source boards thus can be satisfactorily cooled even inthe area subjected to the influence of high temperature air exhaust fromthe light source unit 60.

The air suction inlet of the exhaust fan 86 is surrounded by a surfaceof the main PFC power source board 80 a on which electrical elementssuch as a coil, a capacitor and a resistor are arranged, a surface ofthe sub PFC power source board 80 b on which such electrical elementsare arranged, and the cover surface 81 b. Thereby, the low temperatureair taken from the air inlet 84 can be brought into contact with theelectrical elements such as the coil and the capacitor that generateheat, and the PFC power source boards can be efficiently cooled.

In the present embodiment, since the sub PFC power source board 80 b isdisposed orthogonal to the surface of the main PFC power source board 80a, the apparatus can be downsized compared to when the main PFC powersource board 80 a and the sub PFC power source board 80 b are arrangedside by side such that the main PFC power source board 80 a surface andthe sub PFC power source board surface are parallel.

In the above description, the power source unit 80 has a shape thatcauses the sub PFC power source board to face the cover surface 81 b.However, another arrangement is possible so that the sub PFC powersource board 80 b faces the main PFC power source board 80 a. With thisarrangement as well, the main PFC power source board 80 a and the subPFC power source board 80 b can surround the flow path of the air, andthe entire PFC power source boards can be satisfactorily cooled. A greatnumber of electrical elements such as coils extending in the directionorthogonal to the board surface are attached to the main PFC powersource board 80 a and the sub PFC power source board 80 b. Thus, whenthe sub PFC power source board 80 b is arranged to face the main PFCpower source board 80 a, the electrical elements on the main PFC powersource board 80 a and the electrical elements on the sub PFC powersource board 80 b are arranged to be one over the other with respect toa direction of the airflow toward the exhaust fan 86. As a result, theair flowing toward the exhaust fan 86 may hit electrical elements, andthe airflow in the space surrounded by the main PFC power source board80 a and the sub PFC power source board 80 b may be hindered. On theother hand, when the sub PFC power source board 80 b is arranged to beorthogonal to the main PFC power source board 80 a, the air can flow tothe exhaust fan 86 without hitting the electrical elements at least in alower area near the cover surface 81 b (an area apart from the main PFCpower source board 80 a) in the space surrounded by the main PFC powersource board 80 a, the sub PFC power source board, and the cover surface81 b. Therefore, the airflow in the space surrounded by the main PFCpower source board 80 a, the sub PFC power source board 80 b, and thecover surface 81 b can be improved so that effective and efficientcooling can be carried out compared to when the sub PFC power sourceboard 80 b is arranged to face the main PFC power source board 80 a.

FIGS. 30A and 30B perspectively illustrate the ballast board unit 3.

As illustrated in FIGS. 30A and 30B, the ballast board unit 3 includes aballast board holder 3 b for holding the ballast board 3 a. Ventilationholes 3 c are provided on the bottom surface of the ballast board holder3 b.

FIG. 31 perspectively illustrates a state that the ballast board unit 3is removed from the main body.

As illustrated in FIG. 31, the power source air inlets 56 are arrangedat a part of the base member 53 beneath an area where the ballast boardunit 3 is to be mounted. The ballast board unit 3 is attached to themain body so that the ventilation holes 3 c of the ballast board holderface the power source air inlets 56 and the ballast board 3 a faces thelight source housing 97.

The air suctioned by the suction force of the exhaust fan 86 from thepower source air inlets 56 rises between the light source housing 97 andthe ballast board 3 a, as indicated by an arrow J1 in FIG. 31. Thereby,the light source housing 97 and the ballast board 3 a can be cooled.Furthermore, as indicated by an arrow J2 in FIG. 31, the air flows intothe space surrounded by the main PFC power source board 80 a, the coversurface 81 b, and the sub PFC power source board 80 b. After cooling thePFC power source boards 80 a and 80 b, the air is then discharged to theoutside of the apparatus from the exhaust fan 86, as indicated by anarrow J3 in FIG. 31.

Therefore, in the present embodiment, the ballast board 3 a and the PFCpower source boards 80 a, 80 b can be efficiently cooled, since the airfor cooling the ballast board 3 a is flowed to the space surrounded bythe main PFC power source board 80 a, the cover surface 81 b, and thesub PFC power source board 80 b to also cool the PFC power source boards80 a, 80 b.

FIG. 32 is a block diagram illustrating power supply.

As illustrated in FIG. 32, the sub PFC power source board 80 b includesa PFC switch unit 183 and a starting voltage converter 184 forconverting the AC voltage supplied from a power source cable 190 to theDC voltage and supplying the DC voltage of 3.3V to the control board 2.

The main PFC power source board 80 a includes a control voltageconverter 185 for converting the AC voltage supplied from the powersource cable 190 to the DC voltage and supplying the DC voltage of 12 Vto the control board 2, a ballast switch unit 186, and a booster 187 forboosting the AC voltage of 100 V to 380 V. In the present embodiment,the power source unit 80 is configured by a plurality of boards, asillustrated in FIG. 32. However, the same effect can be obtained even ifthe ballast board 3 a, which is the power stabilizing unit forstabilizing the power to the light source 61, is divided into aplurality of boards. One of the divided ballast boards 3 a and the mainPFC power source board 80 a may form the two surfaces of the flow path.

When a plug of the power source cable 190 is inserted to an outlet orsocket and the AC voltage is applied to the sub PFC power source board80 b, the DC voltage of 3.3 V is applied from the starting voltageconverter 184 to the control board 2. When the DC voltage of 3.3 V isapplied, the control board 2 turns ON the PFC switch unit 183 of the subPFC power source board 80 b after determining that the apparatus is in anormal state by examining for example the temperature detected with atemperature detection unit such as a thermistor arranged at apredetermined position of the apparatus and the like.

When the PFC switch unit 183 is turned ON, the AC voltage from the powersource cable 190 is supplied to the main PFC power source board 80 a.When the AC voltage is supplied to the main PFC power source board 80 a,the DC voltage of 12 V is applied from the control voltage converter 185to the control board 12 V. When the DC voltage of 12 V is applied, thecontrol board 2 turns ON the ballast switch unit 186 of the main PFCpower source board 80 a if the light source 61 and the like are notfound to be abnormal as a result of checking for example the temperatureof the light source 61 and the like.

When the ballast switch unit 186 of the main PFC power source board 80 ais turned ON, the AC voltage from the power source cable 190 is appliedto the booster 187, the AC voltage is boosted to 380 V in the booster187, and the voltage of 380 V is applied to the light source 61 whilecontrolling such that a stabilized power (current) is supplied to thelight source 61 by the ballast board 3 a. The light source is therebylighted.

The above explanations are only examples. The present invention hasspecific effects for each of the following aspects (1) to (8) includingembodiments.

(1)

An image projection apparatus is provided with a light source, lightfrom which is used to form an image to be projected, a first flow path,a control unit configured to control a light emission from the lightsource, an electrical power stabilizing unit configured to stabilize anelectrical power to be supplied to the light source, and an electricalpower source unit configured to supply the electrical power to at leastone of the control unit and the electrical power stabilizing unit. Oneor both of the electrical power source unit and the electrical powerstabilizing unit is/are divided into a plurality of boards. The lightsource is arranged on a normal line of a surface of any of the pluralityof boards (the sub PFC power source board 80 b in the presentembodiment). The plurality of boards configure surfaces of the firstflow path except a surface nearest to the light source.

According to the configuration as such, components to form only the flowpath are not required. Thus, the number of components can be reduced.The boards relating to the electrical power source can be accommodatedin a small space. Thereby, the apparatus can be downsized, since thereis no need for preparing a large space for accommodating boards relatingto electrical power source, and a space which has been conventionally adead space can be efficiently used.

(2)

The image projection apparatus described in (1) is provided with a caseconfigured to accommodate the light source, a projection optical partincluding a reflecting surface to form a projection image of the imageformed by using the light from the light source, and the plurality ofboards. A second flow path is formed at least by one side surface of thecase and a back surface of the reflecting surface. The second flow pathis fluidically connected with the first flow path. None of the pluralityof boards configures a surface of the first flow path near the one sidesurface of the case.

According to the configuration as such, the airflow from the air inlet84 to the exhaust outlet 85 is not hindered by the boards.

(3)

In the image projection apparatus described in (1) or (2), the pluralityof boards are arranged so that their surfaces on which one or moreelectrical elements is/are disposed face inward of the first flow path.

According to the configuration as such, electrical elements includingcoil, capacitor and the like which generate heat on the boards can becooled directly by the air. Thus, entire electrical power source boardscan be efficiently and effectively cooled.

(4)

In the image projection apparatus described in any of (1) to (3), one ofthe plurality of boards (the sub PFC power source board 80 b in thepresent embodiment) has a thermal switch 182 to shut off the electricalpower to be supplied to the plurality of boards, when it becomes apredetermined temperature or more. The power source board provided withthe power switch 182 is disposed above the light source 61.

According to the configuration as such, the following effect can beobtained. The air around the light source 61 is heated because of theheat radiation from the light source 61 when the light source 61 becomesabnormally high temperature. The heated air rises upward to heat thethermal switch 182. As a result, the thermal switch 182 becomes thepredetermined temperature or more, and shuts off the electrical power tobe supplied to the power source boards. Thereby, the light source 61 canbe prevented from being continuously used while it becomes abnormallyhigh temperature. Thus, the safety of the image projection apparatus canbe more improved.

According to the present invention, the power source board or theballast board is divided into the plurality of boards to form the flowpath except a surface nearest to the light source. Thereby, the coolingefficiency of the boards can be improved. Therefore, it is possible touse efficiently the space to which heat is likely to be conducted and/orradiated from the light source.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. (canceled)
 2. An image projector, comprising: a light source to emitlight; a fan to make air flow toward an exhaust outlet of the imageprojector; an image generator to generate an image using the light fromthe light source; a concave mirror to reflect the image from the imagegenerator; a circuit board including a surface that faces the air flow;and a cover to cover at least the concave mirror, wherein the air flowpasses between the cover and a rear surface of the concave mirror. 3.The image projector according to claim 2, wherein the circuit boardincludes a power source board and a ballast board.
 4. An imageprojector, comprising: a light source to emit light; a fan to make airflow toward an exhaust outlet of the image projector; an image generatorto generate an image using the light from the light source; a concavemirror to reflect the image from the image generator; and a circuitboard including a surface that faces the air flow, wherein the air flowpasses through a path defined by at least a rear surface of the concavemirror.
 5. The image projector according to claim 4, further comprising:an exterior cover of the image projector, wherein the path is defined bythe rear surface of the concave mirror and the exterior cover of theimage projector which faces the convex rear surface.
 6. The imageprojector according to claim 4, further comprising another circuitboard, wherein surfaces of the circuit boards face the air flow.
 7. Theimage projector according to claim 6, wherein the circuit boards includea power source board and a ballast board.
 8. An optical unit,comprising: a light source to emit light; an image generator to generatean image using the light from the light source; a concave mirror toreflect the image from the image generator; and a circuit board, whereinan air path for cooling the circuit board is defined by at least a rearsurface of the concave mirror.